Diesel-Drive, Untethered Type Prototype Deep Sea Exploration Vehicle Completed
Mitsui Engineering & Shipbuilding Co., Ltd. (MES) and the University of Tokyo have jointly completed the first prototype of an autonomous underwater vehicle (AUV) called R-one Robot which is designed for exploring wide areas of the seafloor as an untethered and self-propelled type.
Use of a diesel-electric drive for propulsion is the most outstanding feature of the robot.
Outline of Diving Operation
MES in August, 1996 succeeded in four-hour, approximately 20km continuous diving of the "R-one Robot" which had been jointly developed with the underwater robot research group of the Institute of Industrial Science, University of Tokyo. The robot measured such environmental and oceanographical factors as pH, water temperature, dissolved oxygen concentration and salt concentration. The "R-one Robot" exactly passed through six preassigned points of different depths in turn. The maximum diving depth was 150m.
The autonomous diving was a full-scale diving operation, following a trial diving session carried out in July, year in a shallow-water area off the coast of Tamano City, Okayama Pref., and the first success in the world as an AUV powered by a closed cycle diesel engine (CCDE) system. The diving period and distance were the longest record of AUV run in Japan.
During the three-day tests, the "R-one Robot" dived nine times for a cumulative duration of some ten hours, and thereby demonstrated its ability to dive over a distance of 120km. Its stable motions also endorsed its practical usefulness as a platform for long-dislance continuous subsea observation.
Outline of "R-one Robot"
1. The "R-one Robot" is the world's first autonomous under- water robot equipped with a CCDE system.
2. It can measure underwater environmental factors and survey the ocean bed for 24 continuous hours.
3. It is capable of autonomous navigation with its inertial navigation system without relying on instructions from a mother ship.
4. A large payload space is provided to accommodate various instruments for measuring oceanic environment.
5. It can be used repeatedly only if fuel, liquefied oxygen and carbon dioxide absorbent are supplied, which is expected to reduce the running and construction costs.
6. Main particulars of the robot :
Overall length 8.3m
Hull diameter 1.2m
Total span of horizontal tail fins: 1.8m
Weight in air: 4.4 tons
Maximum diving depth: 400m
Maximum speed: 3.6 knots
Endurance: 24 hours (at 2.3 knots)
Power source: Closed cycle diesel engine system
Main computers: MC68040×2
CCDE
This is a system to remove carbon dioxide, soot and water vapor from the engine exhaust, and add oxygen to the cleaned exhaust to make it the intake gas. The CCDE runs independent of the environment, thus it can be used in closed space such as water or a tunnel. Potassium hydroxide solution is used to absorb the carbon dioxide. Although some CCDEs for underwater use have been studied in many countries, the "R-one Robot" represents the only instance of successful application of this system to an autonomous underwater robot in the world.
Future Prospects
1. The successful accomplishment of long-hour diving by the "R-one Robot" has endorsed the applicability of autonomous underwater robots to specific subsea activities. They are now expected to prove usefulness not only for observation of the seabed but also for measurement of seawater properties by means of continuous chemical and biological measurement at a high space resolution ability beyond any conventional method. It is also expected to open a new page in high-density continuous measurement, which oceanologists all over the world are trying to achieve in connection with weather changes in global dimensions.
2. The University of Tokyo's research group is planning to strengthen the autonomy of the "R-one Robot" as well as to dive it actively in seas.
3. It is expected that the reliability and practical usefulness of the CCDE system be well demon-
